OpenPurchaseOrderUseCase.cs

public class OpenPurchaseOrderUseCase : IOpenPurchaseOrders
{
    public OpenPurchaseOrderUseCase(
        IPurchaseOrderRepository purchaseOrderRepository, 
        IPublishPurchaseOrderEvents purchaseOrderEventPublisher)
    {
        this.purchaseOrderRepository = purchaseOrderRepository;
        this.purchaseOrderEventPublisher = 
            purchaseOrderEventPublisher;
    }

    void OpenNewPurchaseOrder(PurchaseOrderRequest input)
    {
        // other code excluded for brevity
        var newPurchaseOrder = Process(input);
        purchaseOrderRepository.Create(newPurchaseOrder);
        purchaseOrderEventPublisher.Publish(newPurchaseOrder.Events);
    }
}